Minyi Han

High pressure processing alters water distribution enabling the production of reduced-fat and reduced-salt pork sausages.

High pressure processing (HPP) was used to explore novel methods for modifying the textural properties of pork sausages with reduced-salt, reduced-fat and no fat replacement additions. A 2×7 factorial design was set up, incorporating two pressure levels (0.1 or 200 MPa) and seven fat levels (0, 5, 10, 15, 20, 25 and 30%). Sausages treated at 200 MPa exhibited improved tenderness at all fat levels compared with 0.1 MPa treated samples, and the shear force of sausages treated at 200 MPa with 15 or 20% fat content was similar to the 0.1 MPa treated sausages with 30% fat. HPP significantly changed the P₂ peak ratio of the four water components in raw sausages, resulting in improved textural properties of emulsion-type sausages with reduced-fat and reduced-salt. Significant correlations were found between pH, color, shear force and water proportions. The scanning and transmission micrographs revealed the formation of smaller fat globules and an improved network structure in the pressure treated sausages. In conclusion, there is potential to manufacture sausages with reduced-fat and reduced-salt by using HPP to maintain textural qualities.

Effects of the sugarcane dietary fiber and pre-emulsified sesame oil on low-fat meat batter physicochemical property, texture, and microstructure

The purpose of this study was to evaluate the effects of sugarcane dietary fiber (SDF) and pre-emulsified sesame oil for pork fat replacement on batter characteristics. Replacing pork fat with SDF and pre-emulsified sesame oil significantly affected color, water- and fat-binding properties, texture, dynamic rheology, microstructure and sensory analysis. With SDF and pre-emulsified sesame oil, the batters had improved textures and gave good sensory scores. These batters containing SDF had reduced the cholesterol and fat contents. With increasing levels of SDF, the batters had higher water- and fat-binding properties, improved texture (hardness, gumminess and chewiness), dynamic rheology and a more balanced nutritional composition. However, when the level of SDF reached 3%, the pores formed by SDF in batter were too large to hinder aggregation and the hardness of batter was unacceptable, which result the allover acceptability to be unsatisfactory. The sample 2% SDF had comparable overall acceptability to the control batter.

Evaluation of protein structural changes and water mobility in chicken liver paste batters prepared with plant oil substituting pork back-fat combined with pre-emulsification.

Protein structural changes and water mobility properties in chicken liver paste batters prepared with plant oil (sunflower and canola oil combinations) substituting 0-40% pork back-fat combined with pre-emulsification were studied by Raman spectroscopy and low-field nuclear magnetic resonance (NMR). Results showed that pre-emulsifying back-fat and plant oil, including substituting higher than 20% back-fat with plant oil increased the water- and fat-binding (p<0.05) properties, formed more even and fine microstructures, and gradually decreased the NMR relaxation times (T21a, T21b and T22), which was related to the lower fluid losses in chicken liver paste batters. Raman spectroscopy revealed that compared with a control, there was a decrease (p<0.05) in α-helix content accompanied by an increase (p<0.05) in β-sheet structure when substituting 20-40% back-fat with plant oil combined with pre-emulsification. Pre-emulsification and plant oil substitution changed tryptophan and tyrosine doublet hydrophobic residues in chicken liver paste batters.

Conformational changes induced by high-pressure homogenization inhibit myosin filament formation in low ionic strength solutions

Myofibrillar proteins (MPs) of chicken breast are generally insoluble in water. We have developed a new method whereby MPs are solubilized in water by applying high-pressure homogenization (HPH) thus potentially enabling greater utilization of meat in various products. To clarify the mechanism of solubilization of MPs by HPH, we investigated their conformation, solubility and filament forming behavior in low ionic strength solutions induced by 15,000psi HPH (103MPa). HPH induces unfolding of MPs which subsequently exposes sulfhydryl and hydrophobic groups to the surface. Our findings, determined by circular dichroism, ATR-FTIR, SDS-PAGE and LC-ESI-MS/MS analysis suggest that HPH leads to unraveling of helical structures and to formation of myosin oligomers through disulfide bond. Due to intermolecular electrostatic repulsion and physical barrier of disulfide bonds in the rod induced by HPH, we suggest that the altered myosin conformation in MPs inhibits filament formation, thus contributing to high solubility of MPs in water.

Reduced functionality of PSE-like chicken breast meat batter resulting from alterations in protein conformation

The objectives of this study were to evaluate protein thermal stability, water-protein interaction, microstructure, and protein conformation between PSE-like and normal chicken breast meat batters. Sixty pale, soft, and exudative (PSE)-like (L*>53, pH24 h<5.7) and 60 normal (46<L*<53, 5.7<pH24 h<6.1) chicken breast meats were selected from 3 different occasions in a major Chinese commercial plant. Two different meat batters were formulated to 14% meat protein and 2% salt, and they were analyzed for the protein changes and the microstructure using differential scanning calorimetry, low-field (LF)-NMR, SEM, and Raman spectroscopy. PSE-like meat batter had lower gel strength, water-holding capacity, and salt-soluble protein extraction (P<0.05). Heated PSE-like meat batter formed an aggregated gel matrix, while normal meat batter produced a compact gel network with fine, cross-linked strands by many protein filaments. LF-NMR revealed an increase in the water mobility in heated PSE-like meat batter with an increasing amount of loosely bound water (P<0.05). No significant changes were observed in the electrophoretic patterns of salt-soluble protein extracts by SDS-PAGE. However, differential scanning calorimetry showed that PSE-like meat had greater myosin and sarcoplasmic proteins/collagen denaturation (P<0.05). In PSE-like meat, actin denaturation was particular evident after salt addition (P<0.05) using differential scanning calorimetry. Moreover, Raman spectroscopy indicated that PSE-like meat batter had less unfolded α-helix and β-sheet structure formation, reduced exposure of hydrophobic and tyrosine residues (P<0.05), and changes in the microenvironment of aliphatic residues and tryptophan, which affected salt-soluble protein extraction, gel properties, and water-holding capacity. In conclusion, the inferior functional properties of PSE-like meat were attributed to not only myosin denaturation, but also actin denaturation after salt addition and different protein structural states.

Solubilisation of myosin in a solution of low ionic strength L-histidine: Significance of the imidazole ring.

Myosin, a major muscle protein, can be solubilised in a low ionic strength solution containing L-histidine (His). To elucidate which chemical constituents in His are responsible for this solubilisation, we investigated the effects of 5mM His, imidazole (Imi), L-α-alanine (Ala), 1-methyl-L-histidine (M-his) and L-carnosine (Car) on particle properties of myosin suspensions and conformational characteristics of soluble myosin at low ionic strength (1 mM KCl, pH 7.5). His, Imi and Car, each containing an imidazole ring, were able to induce a myosin suspension, which had small particle size species and high absolute zeta potential, thus increasing the solubility of myosin. His, Imi and Car affected the tertiary structure and decreased the α-helix content of soluble myosin. Therefore, the imidazole ring of His appeared to be the significant chemical constituent in solubilising myosin at low ionic strength solution, presumably by affecting its secondary structure.

Changes in protein structures to improve the rheology and texture of reduced-fat sausages using high pressure processing

This study investigated the role of high-pressure processing (HPP) for improving the functional properties of meat batters and the textural properties of reduced-fat sausages. Application of 200MPa pressure at 10°C for 2min to pork batters containing various fat contents (0-30%) affected their rheological properties, cooking losses, color, textual properties and their protein imaging. The results revealed that both application of 200MPa and increasing fat content decreased cooking loss, as well as improved the textural and rheological properties. Cooking losses, texture and sensory evaluation of 200MPa treated sausages having 20% fat were similar to those of the 0.1MPa treated sausages having 30% fat. Principal component analysis revealed that certain quality attributes were affected differently by the levels of fat addition and by HPP. These findings indicated the potential of HPP for improving yield and texture of emulsion-type sausages having reduced fat contents.

The use of the impedance measurements to distinguish between fresh and frozen–thawed chicken breast muscle

An impedance system was built to differentiate fresh chicken breasts from those that had been frozen and thawed. Inserting needle electrode pairs of the detecting probe aligned with the longitudinal direction of muscle myofibers (PL) gave more satisfactory results. Learning vector quantization neural network (LVQNN) and partial least square-discriminant analysis (PLS-DA) were employed to acquire the prediction accuracy. The results demonstrated that the model using LVQNN achieved a satisfactory prediction accuracy, with a discrimination accuracy for fresh breasts of 100%. Additionally, the recognition results for a single frozen-thawed cycle were greater than 90%, and for two cycles were greater than 88%. The values obtained from PLS-DA were somewhat lower than for LVQNN, being 100% for fresh samples, in excess of 90% for single frozen-thawed cycle and more than 84% for those that had been multiple frozen-thawed. In conclusion, these results showed that the impedance system is a simple and effective application for the discrimination of fresh chicken breasts from frozen-thawed ones.

An evaluation of the effect of water-misting sprays with forced ventilation on the occurrence of pale, soft, and exudative meat in transported broilers during summer: Impact of the thermal microclimate1

This study investigated the effects of water-misting sprays with forced ventilation on the occurrence of pale, soft, and exudative (PSE) meat in transported broilers during summer combined with the evaluation of the thermal microclimate. To evaluate the thermal microclimate within trucks, temperature (Te), ventilation (VT), and relative humidity (RH) were tracked at different locations using 36 data loggers. Three hundred broilers per load of 2,500 were individually monitored. Three transport test runs were divided into 3 treatment groups: 1) 45 min of transport without rest (T), 2) 45 min of transport with 1 h of rest (TR), and 3) 45 min of transport with 15 min of water-misting sprays with forced ventilation and 45 min of rest (TWFR). Birds were slaughtered in a commercial facility and the meat quality of the chilled carcasses was evaluated by determination of pH, color, drip loss, and cook loss of the pectoralis major (PM) muscle. The Te and enthalpy () of the T group at different regions in the vehicle were significantly different. The Te and of the T group at different regions in the vehicle were significantly different. Compared with PM meat from the T group at different regions of the vehicle, meat from the TWFR group at different regions of the vehicle was significantly different for pH, meat color lightness (L* value), and cook loss. Meat from the TWFR group at different regions of the vehicle was not significantly different for pH, meat color L* value, redness (a* value), yellowness (b* value), or drip loss. The results showed that broilers located at the rear of the vehicle experienced severe conditions of Te, VT, and RH, which resulted in the worst meat quality and the highest incidence of PSE meat. However, application of water-misting sprays with forced ventilation immediately after transport eliminated the effect of different microclimatic regions at different positions and created a relatively comfortable environment that might alleviate stress. Moreover, the water-misting sprays with forced ventilation after transport improved the meat quality and reduced the incidence of PSE meat. Although rest after transport also improved meat quality, the effect was not as significant as water-misting sprays with forced ventilation.

Effects of water-misting sprays with forced ventilation on post mortem glycolysis, AMP-activated protein kinase and meat quality of broilers after transport during summer

Effects of water-misting sprays with forced ventilation on post mortem glycolysis, adenosine monophosphate-activated protein kinase (AMPK) and meat quality of broilers after transport during summer were investigated in the present paper. A total of 105 mixed-sex Arbor Acres broilers were divided into three treatment groups: (i) 45 min transport without rest (T); (ii) 45 min transport with 1 h rest (TR); and (iii) 45 min transport with 15 min water-misting sprays with forced ventilation and 45 min rest (TWFR). Each treatment consisted of five replicates with seven birds each. The results indicated that the water-misting sprays with forced ventilation could mitigate the stress caused by transport under high temperature conditions during summer, which reduced the energy depletion in post mortem Pectoralis major (PM) muscle. This resulted in a higher energy status compared to the T group, which would decrease the expression of phosphorylation of AMPK (p-AMPK). Furthermore, decreased the expression of p-AMPK then slowed down the rate of glycolysis in post mortem PM muscle during the early post mortem period, which in turn lessened the negative effects caused by transport on meat quality. In conclusion, water-misting sprays with forced ventilation may be a better method to control the incidence of the pale, soft and exudative meat in broilers.